Electrochemical investigation of flower-like sodium cobalt phosphate-based materials and activated carbon derived from cocoa pod husks as potential electrode for asymmetric supercapacitor

This study presents a hydrothermal synthesis of a flower-like sodium cobalt phosphate (Co3H18Na4P41O24) material, both in pristine form and as composites with varying masses of graphene foam (GF). The electrochemical performance of these materials is thoroughly investigated, with Co3H18Na4P41O24/10mg GF showing the best specific capacity (52mAh g-1 at 1 A g-1 in 1 M KOH). The kinetic analysis using Dunn's approach indicates that the material's charge storage is predominantly diffusion-controlled (76%). Furthermore, activated carbon derived from cocoa pod husks exhibits promising capacitive performance (148 F g-1 at 1 A g-1). When assembled into a full asymmetric device (Co3H18Na4P41O24/10mg GF as the positive electrode and cocoa pod husk-derived activated carbon as the negative electrode), the device achieves a specific capacity of 23 mAh g-1, an energy density of 18 W h kg-1, and a power density of 0.3996 kW kg-1. Notably, it retains 97.8% of its capacity over 10,000 cycles at 10 A g-1, demonstrating excellent stability. This work highlights the potential of Co3H18Na4P41O24/10 mg GF composites in energy storage applications, particularly in high-performance supercapacitors.